Understanding deforestation impacts on soil erosion rates using 137Cs, 239+240Pu, and 210Pbex and soil physicochemical properties in western Iran

Maral Khodadadi; Christine Alewell; Mohammad Mirzaei; Ehssan Ehssan-Malahat; Farrokh Asadzadeh; Peter Strauss; Katrin Meusburger

doi:10.1016/j.jenvrad.2022.107078

Understanding deforestation impacts on soil erosion rates using ¹³⁷Cs, ^239+240Pu, and ²¹⁰Pb_ex and soil physicochemical properties in western Iran

J Environ Radioact. 2023 Feb:257:107078. doi: 10.1016/j.jenvrad.2022.107078. Epub 2022 Nov 21.

Authors

Maral Khodadadi¹, Christine Alewell², Mohammad Mirzaei³, Ehssan Ehssan-Malahat⁴, Farrokh Asadzadeh⁴, Peter Strauss⁵, Katrin Meusburger⁶

Affiliations

¹ Nuclear Agriculture Research School, Nuclear Science and Technology Research Institute (NSTRI), 31485/1498, Iran; Department of Geology and Environmental Earth Science, Miami University, Oxford, OH, United States. Electronic address: khodadm@miamioh.edu.
² Environmental Geosciences, University of Basel, Bernoullistrasse 30, CH-4056, Basel, Switzerland.
³ Nuclear Science and Technology Research Institute (NSTRI), Karaj, 31485/1498, Iran.
⁴ Department of Soil Science, Urmia University, Urmia, 5756151818, Iran.
⁵ Institute for Land and Water Management Research, Federal Agency for Water Management, Pollnbergstrasse 1, A-3252, Petzenkirchen, Austria.
⁶ Swiss Federal Institute for Forest, Snow, and Landscape Research (WSL), 8903, Birmensdorf, Switzerland.

PMID: 36423536
DOI: 10.1016/j.jenvrad.2022.107078

Abstract

To investigate the effects of converting forests into vineyards typical to Zarivar Lake watershed, Iran, which occurred mainly in the 1970s and 80s, on soil erosion,¹³⁷Cs and ²¹⁰Pb_ex, being mid-and-long-term soil loss tracers, were applied. In Chernobyl-contaminated areas like those found in some parts of Europe and Asia, the proportion of ¹³⁷Cs Chernobyl fallout needs to be determined to convert ¹³⁷Cs inventories into soil erosion rates. To do so, Pu radioisotopes were applied for the first time in Iran. The soil samples were gathered from two adjacent, almost similar hillslopes under natural forest (slope length: 250 m; slope gradient: 20%) and rainfed vineyard (slope length: 200 m; slope gradient: 17%). ¹³⁷Cs/^239+240Pu ratios indicated that 49.8 ± 10.0% of ¹³⁷Cs originated from Chernobyl. The net soil erosion rates derived by ¹³⁷Cs, and ²¹⁰Pb_ex approaches were 5.0 ± 1.1 and 5.9 ± 2.9 Mg ha^-1 yr^-1 in the forested hillslope, and 25.9 ± 5.7 and 32.5 ± 14.5 Mg ha^-1 yr^-1 in the vineyard hillslope, respectively. Both ¹³⁷Cs and ²¹⁰Pb_ex highlighted that deforestation increased soil erosion by around five times. Moreover, the impacts of deforestation on soil physicochemical properties were investigated in surface and subsurface soils. Compared to forested hillslope, soil organic carbon stock in the upper 40 cm of the vineyard reduced by 14 Mg C ha^-1 (29%), 8 Mg C ha^-1 of which was removed by erosion within 35 years, and the remaining have likely been lost via emissions (6 Mg C ha^-1). The vineyard topsoil experienced the most dramatic drops in percolation stability (PS), sealing index, and organic matter by about 55, 51, and 49%, respectively. Among all measured physicochemical properties, PS showed the greatest sensitivity to land-use change. Overall, the present study's findings confirmed that deforestation for agricultural purposes triggered soil loss, deteriorated soil quality and possibly contributed to the reduction of the lake's water quality and climate change.

Keywords: (137)Cs; (210)Pb(ex); (239+240)Pu; Land-use change; Soil organic carbon redistribution; Zarivar lake.

Published by Elsevier Ltd.

MeSH terms

Carbon
Cesium Radioisotopes / analysis
Conservation of Natural Resources
Iran
Lead
Radiation Monitoring*
Soil / chemistry
Soil Erosion
Soil Pollutants, Radioactive* / analysis

Substances

Soil
Cesium-137
Lead
Carbon
Cesium Radioisotopes
Soil Pollutants, Radioactive